Information about the concentration of analytes in gases, liquids, and semisolid materials is required in many fields of science and technology, particularly in the field of medicine. The oxygen content of human blood, for example, provides important clinical information for the treatment of certain conditions and diseases. Although pulse oximeters can provide non-invasive measurement of the extent of oxygen saturation in hemoglobin, they do not give information on the concentration of dissolved oxygen in blood.
For quite some time the state-of the art for measuring oxygen concentration in blood has been the electrode probe based on the reduction of molecular oxygen. Certain electrochemical oxygen sensors, both polarographic and galvanic, have been applied with success to both aqueous and nonaqueous solutions in which oxygen is simply dissolved without the possibility of reaction, and to those in which oxygen can react reversibly, as in blood. There are, however, several drawbacks associated with this technique. Patients undergoing blood gas analysis are subjected to the procedure of withdrawing blood from an artery. The method also lacks the capability for continuous in-situ monitoring.
In current commercial systems, the average turn-around time is on the order of half an hour. In addition, risks exist for infection, contamination, and exposure to viruses during the transferring and handling of blood. A need exists for improved systems and methods which provide more complete and accurate information with respect to blood gases and other analytes and which reduces the associated risks to the patient and the providers of health care.